Instant red lining in neutral

[LC Cnd]

Today hit my local Yamaha dealer and discovered the reed block gaskets are still available round $7 a pair - purchased tout suite. The moto seal - same as 3 Bond? Suspect the same stuff. Cheers! Now I off to ck the carb internals - pesky twins.

[evan_calgary]

Good stuff. Most of the motors I have leak down tested have leaked in and around the reed blocks even with proper gaskets. Bonding goo does the trick once discovered.

[seahorse]

You have not synched your carbs, You need to do that before chasing ghosts.
An 8000 rpm air leak is unlikely.
Ill wager your throttle stops are wound too far in.
Have you actually checked your needles and emulsion tubes. Have you checked that you have the correct cut away/marking slides.
You need to check everything then synchronise your carbs as per the multiple posts on this forum.

[seahorse]

And the outcome?

[LC Cnd]

Now it won't start. Found about 100ml of fuel settled into the bottom of the Microns. Drained and replaced the fiberglass battoning. Not the kinda 'burrbling' I wanted. Going to ck the floats and put back the stock needles for starters.

[LC Cnd]

Found this great advise from RDLC Crazy "Info Page" (Lea's form). Being a newbie a this it appears a bit daunting but going to give er' a go (DIY) with a couple tongue depressors to balance the carbs:

"Balancing carbs: Once you have the new carbs in place, you need to balance them. This is easy, they have a balance screw to make this task a simple one. LC's and Valves have an individual cable into the top of each carb and a idle adjust screw for each slide. To balance these carbs, you will be adjusting the cable adjusters at the top of each carb where the cable enters. These should have a locking nut to keep them from moving once set(you probably saw this in the Haynes manual ). There is a method described on the forum called the "lolly stick" (popsicle) method. I would use 2 pieces of 1/16"wood dowel about 6" long. With the bike level up on the center stand, slide a dowel into each carb inlet under the slides alongside the needle. With the slide closed, the dowel should be held sticking straight out of the carb mouth. As you twist open the throttle, the slides rise. This lets the dowel ends sticking out from the carbs start to point down from horizontal, at an angle relative to the amount the slide is opening. If you get down alongside the bike and look across the carb inlets, you can see if the dowels are at the same angle. If not, adjust the cable adjusters (slide height) so the angle of the sticks are the same. Be sure when they are the same that there is a little cable slack (throttle free-play) with the sticks removed and the slides fully closed.Screw the idle adjust screws in till they just touch the slides. To adjust idle RPM, adjust these screws in or out the same amount on each carb to keep the idle slide position balanced.

Float height: Although this adjustment is done with the carbs off the bike, the best way to confirm that it is correct is to attach a clear piece of tubing to the drain/overflow fitting on the bottom of the carb and use it as a sight glass. Again with the bike level on the center stand, connect the tube and hold it up alongside the carb body. With the fuel supply on(prime position?) and the float bowls full, open the float bowl drain screw. The fuel in the bowl will seek it's own level in the clear tube and you can see where it is in the bowl. The fuel supply will make p the amount sent out into the tube for an accurate level reading in the bowel. It should be within 2MM of where the top of the bowl meets the carb body. This is important as the different circuits draw fuel from different levels in the bowl. If not correct then you must re-bend the tabs on the floats to get it there (float height adjustment in manual).
At this point, if everything is mechanically balanced, you should be able to re-assemble the air intake and any other plumbing and start the bike. The idle will probably be off and require adjustment with the sets crews (remember, both screws at the same time). If you set up the carbs the same as the ones you took off, It should be similar to how it was but it will still require some adjustment and checks before you can declare it safe for the road."

Good stuff - time to get dirty hands see how it works out! On Saturday spoke to a retired Yamaha mechanic who advised I might discover an air leak by spraying DW40 outside the reed gaskets: if you have a change in idle speed from the spraying - bingo you have a leak and a repair. Also the carb needle has settings and I was advise to pick the middle one as a start point. Jetting is the next lesson.

[evan_calgary]

Off topic but...how the heck are you supposed to get a popsicle stick into the stock LC airbox to do this sync?

[hondaror]

Ideally you need a uni-sync to balance the carbs. Measures the vacuum of each barrel while it's running. Mechanical sync is futile, because it is incorrect and only approximate (the best, that most are capable of). A truly sync'd set of carbs creates the best results for a smooth running engine. Major differences here.

[LC Cnd]

Rory which home made manometer or uni-sync balance would you recommend?

1) https://www.youtube.com/watch?v=pGbDOMVfgZA" onclick="window.open(this.href);return false;
2) https://www.youtube.com/watch?v=Y_WDF6glD5k" onclick="window.open(this.href);return false;
3) https://www.youtube.com/watch?v=7D_f05_a74Y" onclick="window.open(this.href);return false;

I personally like the Cororna beer bottle one (#3) but using 2 stoke oil in the balance bottle seems more engine friendly along with 1/8" drill bits instead of popsicle sticks (#2). Once created, where are the vacuum port do I hook it up cause my service manuel does not mention where to install a uni-sync balance. I'm thinking its the other side of the choke. Thx

[RuZty]

Off topic but...how the heck are you supposed to get a popsicle stick into the stock LC airbox to do this sync?

In the UK a 'lolly' is what we call a 'sucker', the ones with plastic sticks work best, but anything rigid and thin will do, solid copper wire etc.
You are just using it as a visual on the slides when viewed from the side, looking straight on makes it hard to focus on both at once. You can do this with the airbox on too if you remove the boots.

[hondaror]

Ideally you want a uni-sync. Looks like an egg yoke separator. I have not been able to find one for sale anywhere. You hold it over the open carb at idle before you assemble the intake filter system. 4 strokes have carb stick locations to tap into for vacuum. 2 strokes do not.

[LC Cnd]

Suspect this is what you were referring to. I found one for $59 plus $5.99 shipping. Lots on eBay for cheaper for bid. Here's one in operation if interested - he's working on a 'Susie' water buffalo GT750. Thought you would have to do them at the same time - appearently not. Don't know if the gent in the video is doing it correct but there you have it.
https://www.google.ca/url?sa=t&rct=j&q= ... 3452,d.amc" onclick="window.open(this.href);return false;

[hondaror]

Bravo, and that is it!

[hondaror]

I just ordered one. Have been trying to find one through work all year. A must have for syncing carbs.

[2smoke]

I`m sorry but syncing carbs has nothing to do with instant redlining in neutral or a no start condition.
No one has mentioned the air screws yet. Are they in place with their springs? How many turns out?
Also, several people have mentioned the choke tube that connects the carbs but you haven't replied if its in place or not. Its a crutial piece.